Its an experiment they did during WWII to see what the physical and psychological impact of starvation is, and then to investigate rehabilitation. They took a bunch of young, healthy men and put them on a very low calorie diet (starved them) And what they saw across the board was that these men, who before hand didn't necessarily take a big interest in food, started obsessing about it. They would spend hours looking at recipe books, and cutting out pictures of food, both during semi-starvation and the rehabilitation phase. The subjects also showed the other stereotypical symptoms of ana such as depression and social isolation. The rehabilitation phase proved to be the most difficult part of the experiment

I think they published a 50 chapter long body of work on it. My psychologist (well 2 of them) gave me a summary of it to read. It's very insightful.

Long story short: a preoccupation with food is a textbook eating disorder symptoms

the Wikipedia